A Bifunctional Chemomechanics Strategy To Suppress Electrochemo-Mechanical Failure of Ni-Rich Cathodes for All-Solid-State Lithium Batteries.

Electrochemo-mechanical failure of Ni-rich cathodes leads to rapid performance degradation, and thus hinders their practical implementation in all-solid-state lithium batteries (ASSLBs). To solve this problem, herein, we propose a bifunctional chemomechanics strategy by protecting polycrystalline LiNi0.6Co0.2Mn0.2O2 (NCM) cathodes using a high-mechanical-strength fast ionic conductor LiZr2(PO4)3 (LZP) coating layer. The coating layer's synergistic effect between mechanical strength and electrochemical stability is studied in Li6PS5Cl (LPSCl)-based ASSLBs for the first time. Using finite element method (FEM) simulations and various characterization techniques, we demonstrate that the robust and stable LZP (Young's modulus 140.7 GPa, electrochemical stability window >5 V) coating layer mitigates the volume change and particle disintegration of polycrystalline NCM and electrochemical decomposition of LPSCl on the LPSCl/NCM interface. As a result, the LZP-modified ASSLBs display remarkably improved reversible capacity, cycle life, and rate performance. The synergy of mechanical and electrochemical properties of the coating layer will provide valuable guidance for the development of high-energy-density ASSLBs.

LiDFOB Initiated In Situ Polymerization of Novel Eutectic Solution Enables Room-Temperature Solid Lithium Metal Batteries.

It is demonstrated that a novel eutectic solution including 1,3,5-trioxane (TXE) and succinonitrile (SN) can be converted into solid-state polymer electrolyte (SPE) via in situ polymerization triggered by lithium difluoro(oxalato)borate (LiDFOB). It is worth noting that all the precursors (LiDFOB, TXE, and SN) of this novel SPE are totally solid and nonvolatile at room temperature, where, LiDFOB works as a lithium salt and an initiator simultaneously to avoid the introduction of impurity. It is noted that such SPE presents a considerable ionic conductivity of 1.14 × 10-4 S cm-1 and a sufficiently wide electrochemical window of 4.5 V, which is significant for supporting the high-energy lithium batteries. In addition, this dedicatedly designed in situ polymerization is powerful to build kinetically favorable polymer-based protective layers on LiCoO2 cathode and Li metal anode simultaneously, guaranteeing outstanding cycling stability (capacity retention of 88% after 200 cycles) of 4.3 V LiCoO2/lithium metal batteries at room temperature. More intriguingly, soft packed LiCoO2/SPE/Li metal batteries can still light a blue light emitting diode (LED) under the harsh conditions of being bent, cut, and stroked by a hammer, demonstrating excellent safety characteristics.

In-situ visualization of the space-charge-layer effect on interfacial lithium-ion transport in all-solid-state batteries.

The space charge layer (SCL) is generally considered one of the origins of the sluggish interfacial lithium-ion transport in all-solid-state lithium-ion batteries (ASSLIBs). However, in-situ visualization of the SCL effect on the interfacial lithium-ion transport in sulfide-based ASSLIBs is still a great challenge. Here, we directly observe the electrode/electrolyte interface lithium-ion accumulation resulting from the SCL by investigating the net-charge-density distribution across the high-voltage LiCoO2/argyrodite Li6PS5Cl interface using the in-situ differential phase contrast scanning transmission electron microscopy (DPC-STEM) technique. Moreover, we further demonstrate a built-in electric field and chemical potential coupling strategy to reduce the SCL formation and boost lithium-ion transport across the electrode/electrolyte interface by the in-situ DPC-STEM technique and finite element method simulations. Our findings will strikingly advance the fundamental scientific understanding of the SCL mechanism in ASSLIBs and shed light on rational electrode/electrolyte interface design for high-rate performance ASSLIBs.

A Novel Bifunctional Self-Stabilized Strategy Enabling 4.6 V LiCoO2 with Excellent Long-Term Cyclability and High-Rate Capability.

Although the theoretical specific capacity of LiCoO2 is as high as 274 mAh g-1, the superior electrochemical performances of LiCoO2 can be barely achieved due to the issues of severe structure destruction and LiCoO2/electrolyte interface side reactions when the upper cutoff voltage exceeds 4.5 V. Here, a bifunctional self-stabilized strategy involving Al+Ti bulk codoping and gradient surface Mg doping is first proposed to synchronously enhance the high-voltage (4.6 V) performances of LiCoO2. The comodified LiCoO2 (CMLCO) shows an initial discharge capacity of 224.9 mAh g-1 and 78% capacity retention after 200 cycles between 3.0 and 4.6 V. Excitingly, the CMLCO also exhibits a specific capacity of up to 142 mAh g-1 even at 10 C. Moreover, the long-term cyclability of CMLCO/mesocarbon microbeads full cells is also enhanced significantly even at high temperature of 60 °C. The synergistic effects of this bifunctional self-stabilized strategy on structural reversibility and interfacial stability are demonstrated by investigating the phase transitions and interface characteristics of cycled LiCoO2. This work will be a milestone breakthrough in the development of high-voltage LiCoO2. It will also present an instructive contribution for resolving the big structural and interfacial challenges in other high-energy-density rechargeable batteries.